U.S. Patent Publication No. 2012/0034150 A1, published Feb. 9, 2012, the disclosure of which is hereby incorporated herein in its entirety by this reference, discloses background information hereto.
Continuous production of solid products from reactive gases typically entails reacting the reactive gases in the presence of a catalyst in such a way that the solid products are elutriated from the surface of the catalyst. The solid products are thus swept away from the catalyst and subsequently harvested in a suitable process or series of processes for removing particulates from reaction tail-gases. Reactors conventionally used for such continuous solid production include fluidized-bed reactors, fixed bed reactors, pulsed bed reactors, shaft kilns, etc. Particulate removal devices typically include cyclones, bag houses, electrostatic precipitators, scrubbers, etc.
The capital and operating expenses of the equipment to separate solid products from tail gases are significant. Worker and environmental exposure associated with maintenance of such equipment are also of concern. In particular, small solid materials such as nanoparticles, fibers, and other morphologies, are very difficult to economically separate from gases because they may be so small that they have high blow-by rates in cyclones, tend to penetrate and plug fabrics in bag filters, and have electrical conductivities making them unsuitable for removal in scrubbers or precipitators.
Efficiently separating solid particles from process gas streams is important for both the economics of a process and for environmental safety of the process. In processes in which the solid product is salable, increasing recovery may be desirable to maximize yield, revenue, or profits. The cost of recovery can be significant in both capital and operating costs. Furthermore, regulatory, safety, or other considerations may dictate limiting or minimizing environmental and worker exposure to industrial dusts and nanoparticles.